Improving Nitrogen Fertilizer Management in Sprinkler-Irrigated Cotton

IPNI-2015-USA-AZ09

01 Mar 2015

Project Description


Water and nitrogen (N) are the first and second constraints to cotton production in the western U.S, respectively (Morrow and Krieg, 1990). Great strides have been made in improving surface irrigation management and water application uniformities in the western US, with the wide adoption of laser leveling. However, the more efficiency overhead sprinkler and subsurface drip irrigation is slowly being adopted in western states like Arizona. Nitrogen fertilizer management research is needed in these systems. Our previous research showed that in surface-irrigated cotton, N fertilizer recovery was still < 50 %. Historically, petiole NO3 is used in the western US for managing in-season N fertilizations, but improved N monitoring is needed. Recently there have been great advances in the development of light-weight spectroradiometers. Canopy reflectance-based N management research using these spectroradiometers in West Texas demonstrated that N fertilizer use can be reduced without hurting lint yields. Canopy reflectance may be a more accurate method of assessing cotton plant N status than petiole NO3 and is definitely a more rapid and appealing approach.

We will also test urea ammonium nitrate plus the nitrification and urease inhibitor Agrotain Plus. This is because we hypothesize that Agrotain Plus will reduce deep leaching, ammonia volatilization and denitrification compared to urea ammonium nitrate alone. Additionally, we will compare reflectance-based N fertilizer management with soil test-based management. The study we be conducted in Maricopa, AZ on a Casa Grande sandy loam.

Nitrogen management and N balance research on cotton in the western US has slowed down considerably in the last 10 years. Knowledge of plant N recovery efficiency, NO3 leaching and denitrification, however, is scant for these systems and new information is greatly needed. Learning the extent of losses and the current N recovery efficiency in sprinkler-irrigated cotton can lead us in the direction of improving NUE and reducing N fertilizer export to the atmosphere and groundwater. We also propose to construct the N balance for the sprinkler-irrigated field. Improving NUE would allow lower rates of N fertilizer to be used by producers without hurting lint yields or fiber quality. Greater profits will be realized for irrigated producers in this time of high N fertilizer prices. The environment is also protected when NUE is improved, especially reductions in NO3- leaching to groundwaters and surface waters, and greenhouse gas forcing is reduced as well.

Background:
Following water, N fertilizer is the main constraint to cotton production in the western USA (Morrow and Krieg, 1990). Canal infrastructure of irrigation water in Arizona means basin, flood, and furrow irrigation are still the pre-dominant choices of irrigation methods. Navarro et al. (1997) in Arizona, and Booker et al. (2007) and Bronson et al. (2007;2008) in Texas reported that recovery efficiency ground-based N applications in furrow-irrigated cotton ranged from only 15 to 34 %. With declining water resources and competition from growing urban areas there is renewed interested in center-pivot or linear-move overhead sprinkler irrigation systems. However, N management research and recommendations in the far western US are lacking for sprinkler irrigation. In the western US, weekly petiole NO3 sampling and analysis is the recommended approach to monitor in-season cotton plant N status. However, petiole sampling is laborious and laboratory turn-around is time-consuming. Additionally, petiole NO3 analysis can be highly variable (Bronson et al. 2001). Canopy reflectance, on the other hand is a rapid, non-destructive method to assess in-season cotton N status (Chua et al., 2003; Bronson et al, 2003). Canopy reflectance-based N management in subsurface drip systems in Texas resulted in reduced N fertilizer use, without hurting lint yields (Yabaji et al., 2009). In that research, N fertilizer was initially applied at half the rate of a regional soil test based recommendation. When normalized difference vegetative index (NDVI, a common remote sensing vegetative index) in the reflectance treatment fell below NDVI of the soil test/adequately fertilized plot, N fertigation was increased. This simple “sufficiency index” approach has not been tested in the western US in sprinkler-irrigated cotton.

We propose and improved and updated N fertilizer management recommendation for 4-bale/acres cotton based on a 36-inch NO3-N soil test. We will also compare UAN with UAN plus the N loss inhibitor Agrotain Plus. Additionally, we will compare reflectance-based N fertilizer management with soil test-based management. The study we be conducted in Maricopa, AZ on a Casa Grande sandy loam.

Objectives:
    1. Compare soil test-based N fertilizer management with two canopy reflectance-based UAN-N management approaches in sprinkler-irrigated cotton.
    2. Compare urea ammonium nitrate (UAN) and UAN with Agrotain Plus in sprinkler-irrigated cotton.
    3. Construct N balances for sprinkler-irrigated cotton, i.e. quantify total N uptake, recovery N use efficiency, NO3 leaching, and denitrification losses.

Plan of work:
In March, 2015, pre-plant soil sampling to 180 cm for NO3 will be done on four samples per plot. Cotton will be planted in April, 2015 in plots that will be 6, 1-m rows wide by 36 m. At harvest, soil sampling to 180 cm for nitrate will on four samples per plot. Nitrogen treatments will include:

Nitrogen treatmentFertilizer sourceNotes
    1. Zero-N
    2. Soil test-based N†
Urea amm. nitrateIn three splits, first square and first bloom and mid bloom†
    3. 1.3*Soil test-based N†
Urea amm. nitrateIn three splits, first square and first bloom and mid bloom†
    4. Soil test-based N†
Urea amm. nitrate + Agrotain PlusIn three splits, first square and first bloom and mid bloom†
    5. Reflectance-based N-1‡
Urea amm. nitrateIn three splits, first square and first bloom and mid bloom‡
    6. Reflectance-based N-2§
Urea amm. nitrateIn three splits, first square and first bloom and mid bloom§
    7. Reflectance-based N-3‡
Urea amm. nitrate + Agrotain PlusIn three splits, first square and first bloom and mid bloom‡
    8. Reflectance-based N-2§
Urea amm. nitrate + Agrotain PlusIn three splits, first square and first bloom and mid bloom‡
† Based on lint yield goal of 4.0 bale/ac, and a 200 lb N/ac N requirement, minus 0 - 36 in. soil NO3-N and estimated irrigation input of 20 lbN/ac (estimated 40 inch irrigation of 2 ppm NO3-N water).
‡ First split equals 50 % treatment no. 2, second and third splits based on NDVI relative to treatment no. 2.
§ First split equals 50 % treatment no. 2, second and third splits based on NDVI relative to treatment no. 3.


Nitrogen will be applied with a high clearance tractor with spoke-wheel applicators on the side of the bed, just prior to an irrigation. Irrigation will be 2-3 times a week with FAO crop coefficients and 90 % ET.

The experimental design will be completely randomized block, with three replicates.

Canopy reflectance we be measured week from first square to first open boll using Crop Circle ACS-470 active sensor. Several vegetative indices will be calculated including NDVI, CCCI, and NDRE. Amber NDVI will be used for reflectance-based N treatments.

Surface flux of N2O will be measured weekly for 10 weeks during the season using vented chambers and gas chromatography. Biomass and total N uptake will be determined plants on 2 m of row at first open boll. Nitrogen recovery efficiency, physiological N use efficiency and agronomic use efficiency will be calculated. Lint and mature seed yields will be machine harvested. Mature cotton seed N will be determined from grab samples at the three DGPS points per plot and the percentage of seed N to total N uptake calculated. Micronaire and other fiber quality attributes will be determined on lint and the relationships of these to N fertilizer rate estimated. Soil sampling for extractable NO3-N from 0 to 180 cm will be done after harvest to assess residual and NO3 and leached NO3 (90 – 180 cm profile NO­3). Post-harvest soil sampling will on four samples per plot to assess the spatial variation of leached NO3 across the plot.

Pre-plant and harvest soil profile NO3, N2O emission, NDVI, plant biomass, plant N uptake, lint, and seed yield will be analyzed with a mixed model using SAS. Replicate will be considered random, and N treatment will be considered fixed. The two subsamples per plot will be averaged by plot in the mixed analysis to produce least square means, but longitude, latitude and longitude*latitude will be covariates.

References:
Booker, J.D., K.F. Bronson, C.L. Trostle, J.W. Keeling, and A. Malapati. 2007. Nitrogen and phosphorus fertilizer and residual response in cotton-sorghum and cotton-cotton sequences. Agron. J. 99:607-613.
Bronson, K.F. 2008. Nitrogen Use Efficiency Varies with Irrigation System. Better Crops with Plant Food. 92 (4): 20-22.
Bronson, K.F., A.B. Onken, J.W. Keeling, J.D. Booker, and H.A. Torbert. 2001.
Nitrogen response in cotton as affected by tillage system and irrigation level. Soil Sci. Soc. Am. J. 65: 1153-1163.
Bronson, K.F., T.T. Chua, J.D. Booker, J.W. Keeling, and R.J. Lascano. 2003. In-season nitrogen status sensing in irrigated cotton: II. Leaf nitrogen and biomass. Soil Sci. Soc. Am. J. 67:1439-1448.
Bronson, K.F., J.C. Silvertooth, and A. Malapati. 2007. Nitrogen fertilizer recovery efficiency of cotton for different irrigation systems. 2007 Proceedings Beltwide Cotton Conferences. [CD-ROM computer file]. National Cotton Council of America, Memphis, TN.
Chua, T.T., K. F. Bronson, J.D. Booker, J.W. Keeling, A.R. Mosier, J.P. Bordovsky, R.J. Lascano, C.J. Green, and E. Segarra. 2003. In-season nitrogen status sensing in irrigated cotton: I. Yield and nitrogen-15 recovery. Soil Sci. Soc. Am. J. 67:1428-1438.
Morrow, M.R. and D.R. Krieg. 1990. Cotton management strategies for a short growing season environment: water-nitrogen considerations. Agron. J. 82:52-56.
Navarro, J.C., J.C. Silvertooth, and A. Galadima. 1997. Fertilizer nitrogen recovery in irrigated Upland cotton. A College of Agriculture Report. Series P-108, University of Arizona, Tucson, AZ. p. 402-407.
Yabaji, Rajkumari, J.W. Nusz, K. F. Bronson, A. Malapati, J. D. Booker, R.L. Nichols, and T. L. Thompson. 2009. Nitrogen management for subsurface drip irrigated cotton: Ammonium thiosufalte, timing, and canopy reflectance. Soil Sci. Soc. Am. J. 73:589-597.

Expected output:
· Improved methods of assessing in-season cotton plant N status in sprinkler-irrigated cotton.
· Assessment of Agrotain Plus for improved yields, and plant N fertilizer recovery in sprinkler-irrigated cotton.
· Improved liquid N fertilizer application technique for sprinkler-irrigated cotton.
· Updated and improved information on the fate and cycling of N fertilizer in sprinkler-irrigated cotton.
· Mitigation of NO3- leaching, N2O emissions and other N loss pathways in sprinkler-irrigated cotton.
· Updated and improved Nitrogen fertilizer recommendations for cotton in Arizona.
    Proposed start date: January 1, 2015, proposed finish date: December 31, 2015.